1. Field of the Invention
The invention relates to a method for connecting a turbine blade or vane to a turbine disk or a turbine ring for a turbine stage of a turbomachine, in particular of a thermal gas turbine. The invention furthermore relates to a turbine stage for a turbine of a turbomachine.
2. Discussion of Background Information
Such a method for connecting a turbine blade or vane to a turbine disk or a turbine ring and also such a turbine stage comprising a turbine disk or a turbine ring which is connected at least indirectly to one or more turbine blades or vanes are known from the prior art. The turbine stage serves for its part for arrangement in a single-stage or multi-stage turbine of a turbomachine formed, in particular, as a thermal gas turbine. Progression in the construction of gas turbines in this respect places ever higher demands on the materials used, however. The turbine blades or vanes serving as guide vanes or rotor blades are therefore produced substantially as polycrystalline, single-crystal or directionally solidified cast parts made of high-temperature-resistant base alloys. Turbine blades or vanes manufactured from composite materials capable of withstanding high temperatures are likewise known.
However, this configuration has the effect that the turbine blades or vanes cannot be fusion welded or can only be fusion welded with great difficulty. A connection to a turbine disk which can be fusion welded or a corresponding turbine ring, which can be manufactured from a nickel base alloy, is therefore not possible using conventional fusion welding processes and leads to considerable additional costs. Alternatively, friction welding or diffusion welding processes are known for establishing an at least indirect connection between the turbine blade or vane and the turbine disk or turbine ring, but these processes require a high outlay for apparatus. In addition, temperatures which are incompatible for common base alloys may arise in these welding processes.
DE 10 2008 052 030 A1 discloses a method in which firstly a connecting body made of a material suitable for fusion welding is formed on the at least one turbine blade or vane by means of a cold spraying process, and then the connecting body is connected to the turbine disk or the turbine ring by means of a fusion welding process. In this context, a cold spraying process is referred to as a coating process in which the material of the later connecting body is applied to the turbine blade or vane at very high speed in powder form. The connection strength which can be achieved with this method is, however, inadequate for typical turbine applications.
It is an object of the present invention, therefore, to provide a method of the type mentioned in the introduction which achieves a high connection strength with little outlay. It is a further object of the invention to provide a turbine stage which can be produced with little outlay having a turbine disk or a turbine ring and at least one turbine blade or vane connected thereto with a high strength.